#此次购物车优化，主要使用了文件操作的相关方法，有买家入口，和商家入口
一、买家入口
1、买家第一次启动程序输入金额，金额会记录到文件里，再登录就读取文件里保存的金额，买家可以购买商品，按 ‘q’ 退出后显示购买的商品和余额，并保存购买过的商品和余额。
1 global data
2 global userinformation
3 money=''
4 data='data.txt'
5 userinformation='userinformation.txt'
6 mgoods=[]
7 exit_flag = False
8 def shuoppxit(money):
9 if money.isdigit():
10 while not exit_flag:
11 for index, item in enumerate(goods):
12 print(index, item)
13 numbres = input("输入购买商品的序号：")
14 if numbres.isdigit():
15 numbres = int(numbres)
16 if numbres< len(goods) and numbres >=0:
17 money = int(money)
18 numbres_goods=goods[numbres][1]
19 if money >= numbres_goods:
20 money=money-numbres_goods
21 goods[numbres].append('余额')
22 goods[numbres].append(money)
23 print(goods[numbres])
24 mgoods.append(goods[numbres])
25 f = open(userinformation, 'w+', encoding='utf-8')
26 f.write(str(mgoods))
27 f.close()
28 print('购买商品成功:'+goods[numbres][0])
29 print('剩余金钱：\033[31;1m %s \33[0m' % money )
30 else:
31 print('余额不足！')
32 elif numbres=='q' or numbres=='Q':
33 print('你购买的商品如下：')
34 f = open(userinformation, 'r', encoding='utf-8')
35 data2 = f.read()
36 goods2 = eval(data2)
37 for i in goods2:
38 print(i)
39 break
40 else:
41 print('输入错误！！')
42 else:
43 print('输入错误！！,重新输入')
44
45 f = open(data,'r',encoding='utf-8')
46 data2 = f.read()
47 goods = eval(data2)
48
49 f = open(userinformation,'r',encoding='utf-8')
50 data2 = f.read()
51 if data2 !='':
52 usernames = eval(data2)
53 money= usernames[0][3]
54 money=str(money)
55 shuoppxit(money)
56 else:
57 money = input("输入你的钱：")
58 shuoppxit(money)
二、商家入口
1、商家可以添加商品，和修改商品价格
global data
money=''
data='data.txt'
mgoods=[]
exit_flag = False
f = open(data,'r',encoding='utf-8')
data2 = f.read()
goods = eval(data2)
print(goods)
while not exit_flag:
choice=input('1、添加商品 2、修改价格：')
if choice.isdigit():
if choice=='1':
name=input('输入商品名：')
price=input('输入价格：')
mgoods.append(name)
mgoods.append(price)
goods.append(mgoods)
f = open(data, 'w', encoding='utf-8')
f.write(str(goods))
f.close()
print(goods)
else:
for index, item in enumerate(goods):
print(index, item)
numbres = input("输入修改商品的序号：")
if numbres.isdigit():
numbres = int(numbres)
if numbres < len(goods) and numbres >= 0:
jiage = input("输入修改商品价格：")
if jiage.isdigit():
jiage = int(jiage)
goods[numbres][1]= jiage
f = open(data, 'w', encoding='utf-8')
f.write(str(goods))
f.close()
print(goods)
exit_flag=True
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